TW is a gold winner
Free decent advice - you dont often get that (so it is your DUTY not to follow it [joke] )
If the "landlord" - that may not be the seller - ammends covenants -- -
if there is a covenant not to keep pets fr'instance - then the immediate seller cant ammend the covenant to Yes you can.
The landlord, seller, and freeholder you can see by that simple example, the three may be different and of course have different rights.
Are you really doing this without a lawyer ?
Your solicitor should be able to clarify.